Underground storage system



June 12, 1956 1.. R. HUNTER UNDERGROUND STORAGE SYSTEM JNVENTOR.

"W; LIZ/111111391 Filed Jan. 12, 1953 g qk l UNDERGROUND STORAGE SYSTEM Loy R. Hunter, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Application January 12, 1953, Serial No. 330,856

11 Claims. (Cl. 62-4) This invention relates to underground storage systems.

Constantly expanding production of liquefied petroleum gas has created a definite problem in providing suitable storage facilities for this material. Due to the high vapor pressure of liquefied petroleum gas, particularly propane, the cost of storage in surface equipment, such as steel tanks, becomes excessive due to the massive construction required to withstand the vapor pressure of the stored material in a safe manner. This problem becomes extremely acute where it is necessary to store large quantities of such materials during the off-season. In addition to the expense involved, the use of steel tanks is limited by shortages in production.

In order to overcome these difliculties, it has been proposed to store liquefied petroleum gas in porous water bearing formations, in water leached caverns in salt formations, or in abandoned mines in impermeable shale or limestone formations. Further, underground concrete storage tanks and buried sections of pipe have been used to a limited extent in the storage of liquefied petroleum gas.

In accordance with this invention, an underground storage system for liquefied petroleum gas is provided which is capable of storing extremely large quantities of this material at a very small unit cost. Further, a number of operating and safety features are provided to insure a long period of trouble-free operation of the storage system, together with easy and reliable introduction of the material into storage and removal of material therefrom. Such features include a gauging device indicating the amount of material in storage at all times. Finally, the shaft is sealed at a region just above the top of the cavern so that the entire region of the shaft, tunnels, and cavern below the seal is eifective as a storage zone while access can be had by workmen to the region above the seal. Scaling the shaft in this manner facilitates the installation and removal of bottom hole pumps, as will be explained in detail hereafter.

It is an object of the invention to provide underground storage facilities of novel construction and arrangement, said facilities providing storage at a minimum unit cost.

It is a further object to provide a system in which the material can be easily introduced into the storage system and removed therefrom.

It is a further object to provide a system in which the amount of material in storage at any time can be readily determined.

It is a further object to provide an improved structure facilitating the installation and removal of downhole pumps.

tates atent O 2,749,714 Patented June 12, 1956 invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure l is a vertical sectional view, partially in elevation, of the underground storage system of this invention;

Figure 2 is an enlarged vertical sectional view of the shaft;

Figure 3 is a sectional view taken along the line 3-3 of Figure 2 looking in the direction of the arrowns; and

Figure 4 is an enlarged detail view of the liner head and sealing structure associated therewith.

Referring now to the drawings in detail, and particularly to Figure l, the underground storage system of this invention includes one or more underground storage caverns, one of which is indicated by reference numeral 10. It will be understood that each cavern can consist of a large excavated region, as illustrated in Figure l, or, alternatively, the cavern can comprise a series of elongated individual storage chambers of cylindrical or rectangular cross section with the axis of the storage chambers in a horizontal or vertical direction, as desired, all of the chambers defining the cavern communicating with a common tunnel leading to a central shaft in the manner hereinafter explained.

A tunnel 11 connects the cavern 10 with an enlarged shaft 12 extending to the surface, and the bottom region of the shaft preferably extends a short distance below the floor of the tunnel, thereby defining a recess or well 13. It will be understood that, where a plurality of caverns are utilized, each cavern can be connected to the central shaft by a separate, preferably horizontal, tunnel. One such additional tunnel is indicated by reference numeral 11a. The shaft 12 is usually vertical but, where the cavern is formed in the side of a cliff or mountain, the shaft can be inclined, or even horizontal.

The cavern 10 is advantageously formed in an impermeable rock formation, such as a limestone formation. This limestone formation is indicated by reference numeral 14 and extends a short distance above the top of the cavern so that the material in storage is effectively sealed by the limestone formation. In accordance with this invention, a sealing structure 15 is disposed in the shaft to the end that the region of the shaft, tunnels, and caverns below the seal constitutes effectively a single storage vessel. Where the fluid to be stored is propane, it will be understood that the vapor pressure of the material necessitates storage in a closed sealed container which is not accessible to workmen while the material is in storage. Where the sealing structure 15 of this invention is provided, the region of the shaft above the structure is free from vapors of the material being stored and, consequently, access can be had thereto by workmen. For example, a hoist 16 suspended by a cable 17 from a sheave assembly 18 of a derrick 19 can be used to permit workmen to enter the shaft, the hoist being raised and lowered in the shaft by motor driven winch mechanism 20 driving the cable 17. The hoist mechanism can also be used to lift casing or tubing, and to remove the pumps from the shaft, as will become apparent later.

The sealing structure 15 includes a large cylindrical metal liner 22 which is set in a mass 23 of cement or concrete, the lower end of the cement being embedded in and supported by the impermeable formation 14. The liner and its exterior shell of concrete extend upwardly a short distance beyond the formation 14 and, at the top of the liner, a sealing or liner head assembly 24 is provided. It

will be noted that the assembly 24 includes a thick circular metalplate or liner head 25, Figure 4, secured by bolts 26 to an annular ring 27 which fits within the upper end portion of the liner 22. Annular welded portions 28, 28a of wedge-shaped cross section cooperate with the liner 22 and the inclined circumferential edges 29 and 30 of the annular ring 27 to effectively seal the circumferential region where the annular ring 27 abuts the liner 22. A gasket 31 is disposed between and seals the zone of engagementof the metal plate 25 and the annular ring 27. It will be noted that the upper end of the liner is tapered, as indicated at 220, to' provide a tapered seat for the welded portion 28a.

Stored material is removed from the cavern by a pair of similar pump assemblies 33 and 34. Each assembly includes a casing string 35, for example, 8 inches in diameter, supporting a casing head 36 and extending downwardly through the shaft 12 and liner head 25 into the well 13 at the bottom of the shaft, the casing string including a valve 37 above the surface of the ground, a valve 38 just above the liner head 25, and a motor valve 38a just above valve 38. Disposed within the casing string 35 is atubing string 40, for example, 4 inches in diameter, the lower end of which carries a motor-pump assembly 41 incorporating an electric motor 42 and a pump 43 driven thereby. It will be noted that stored material from the cavern can fiow through the tunnel 11 into the well 13 whence it is lifted by the pump 43 thro'ugh the tubing string 40 to the surface. At the surface, the tubing string 40 is provided with a valve 45 which is connected to any suitable facility for utilization of the stored fluid together with a valve 46 closing off the top of the tubing string. An electrical cable 47 extends through the casing head 36 and, thence, downwardly through the annular space between the tubing and casing to the motor 42 to supply electrical current thereto. It will be understood that the casing string 35 is welded, as indicated at 35a, to the liner head 25.

The structure included within the shaft also comprises a pipe 48, for example, 12 inches in diameter, having a valve 49 therein above the surface of the earth and a valve 50 therein just above the liner head 25. A gauging line carrying a float 52 extends downwardly into the lower part of the shaft through the pipe 48 and this pipe is provided, above the valve 49, with a float gauge assembly 53 which enables the position of the fioat in the shaft to be measured and thereby indicates the amount of liquid in storage. Such a float gauge assembly is shown in more detail in the copending application of Leonard P. Meade, Serial No. 314,541 entitled, Underground Storage System, filed October 13, 1952. Pipe 48 is also useful in venting vapors from the underground storage system.

A short section 54 of a cylindrical metal liner is disposed adjacent the top of the shaft and prevents caving the loose formations at the surface of the shaft. In one location suit-able for the construction of an underground storage system in accordance with the invention, the shaft 12 extends 260 feet below the surface of the ground and the tunnels extend from the shaft to the storage caverns which are formed in a limestone or shale formation, the caverns being about 150 feet long and 50 feet in diameter. The liner 22 is 30 feet long and extends from a point about feet below the top of the limestone formation 14 to a point about 10 feet above the top of this formation.

The material to be introduced into storage can pass through a fill line extending through the liner head to a portion of the shaft below the level of the top of the cavern, Preferably and advantageously, however, the material to be stored is introduced through a fill and vent system 60, Figure 1, one such system preferably being provided for each cavern. If desired, the system 60 can serve only as a venting means and not as a filling system in one or more of the storage caverns.

As shown, this system includes a metal casing 61 set in a 'mass 62 of cement or concrete at the surface of the earth, this casing extending downwardly to the top of the cavern 10. A valve 63 at the top of the casing supports a tubing head 64 and a string 65 of tubing extends downwardly through the casing into the cavern. The casing can extend vertically downward to the floor of the cavern. However, preferably, the tubing 65 is secured to a filling pipe 66 suspended from the top of the cavern by suitable supports 6'7, this pipe being provided with perforations 68. The material to be introduced into storage is fed into tubing 65 at the surface in any suitable manner, as by a pump 65a, and the material leaves the perforations 68 in the form of a spray which cools the vapor above the liquid in storage in the cavern and thereby reduces the filling pressure required to introduce material into storage. A valve 69 communicates with the annular space between the tubing 65 and casing 61 to allow venting of vapors from the cavern should the pressure therein become excessive.

To facilitate the removal of motor-pump assemblies 41 when necessary for repair or replacement, a motor valve 38a is provided in each casing 35, above plate 25, preferably above valve 38, as shown. When it becomes necessary to remove one of the pumps, tubing 40 is lifted by winch mechanism 20 and cable 17. When the bottom of assembly 41 is above valve 38a, the valve is closed, thus preventing further passage of vapors from the caverns and lower part of the shaft upward through casing 35. Vapor remaining in the annulus between casing 35 and tubing 40 is bled off through casing head 36, and vapor remaining in the tubing 40 is bled off through valve 46. The assembly 41 is then lifted from the shaft by again raising tubing 40 and removing it in sections. Valve 38a can be any suitable type of motor valve as, for example, diaphragm motor valve actuated by air pressure supplied through a suitable line, not shown. Similarly, when a new pump assembly is to be placed in the shaft, the tubing, with the motor and pump installed on the bottom, is lowered into the casing until the bottom of the pump is immediately above motor valve 38a. At this time, the upper portion of tubing 40 including valves 45 and 46 is installed. Casing head 36 is assembled to provide a sliding seal around tubing 40 and cable 47, after which motor valve 38a can be opened and the tubing string lowered until pump 43 is in place in shaft 12. Casing head 36 is then tightened to provide a seal, the surface dispensing lines are connected, and the pumping unit is again ready for operation.

It will be evident that I have achieved the objects of my invention in providing an underground storage system of large capacity at a very low cost per cubic foot of storage space. The cavern can be readily filled through the assembly or assemblies 60, and the provision of the perforated outlet portions in the filling lines produces a spray which cools the vapors in the cavern and reduces the filling pressure. The motor-pump units can be operated individually or together to withdraw the stored fluid from the cavern, one such unit being available should it become necessary to remove or replace the other unit and the motor-pump units can be readily inserted into and withdrawn from the shaft. The float gauge permits the liquid level in the cavern to be observed at all times, and thereby indicates the amount of material in storage. Finally, the provision of the liner anchored in the hard formation in which the cavern is formed materially reduces the cost of the storage, as compared with an installation where the entire shaft is lined, and access can be had by workmen to the valves and sealing structure by use of the hoist 16.

While the invention has been described in connection with a present, preferred embodiment thereof, it is to be understood that this description is illustrative only and is not intended to limit the invention.

This case is related to Serial No. 320,297, filed November 13, 1952, and Serial No. 314,541, filed October 13, 1952.

I claim:

1. In an underground storage system, in combination, an underground storage cavern, a vertical shaft extending from the surface of the earth to a region adjacent said cavern, a tunnel connecting said shaft with the bottom region of said cavern, a cement-anchored tubular metal liner in said shaft, the upper end of said liner extending slightly above the top of said cavern, the region of the shaft above said liner being in unobstructed communica tion with the atmosphere, a metal plate closing off the top of said liner, means for introducing fluid to be stored into said cavern, a casing extending downwardly through said shaft from the well head to a position below the level of the bottom region of said cavern, and a pump disposed at the lower end of said casing to withdraw fluid from the bottom of said shaft and pump said fluid to the surface.

2. A combination in accordance with claim 1 further comprising a float gauge disposed in said shaft to indicate the fluid level therein and thereby the fluid level in said cavern.

3. In an underground storage system, in combination, an underground storage cavern having at least the top portion thereof defined by a subterranean impermeable formation, a shaft extending from the surface of the earth through said formation to a region adjacent said cavern, a tunnel connecting said shaft with the bottom region of said cavern, means sealing off said shaft at a level adjacent the top of said formation, said sealing means including a tubular metal liner having its lower end extending slightly below the top of said formation and having its upper end extending slightly above the top of said formation, a mass of cement anchoring said liner in position within said shaft, a fiat plate closing off the top of said liner, a casing string extending from the surface downwardly through said shaft and said plate to the level of the bottom of said tunnel, a string of tubing mounted concentrically within said casing string, a motorpump unit carried by said tubing and positioned thereby at the bottom of said casing to lift the fluid from said cavern to the surface through said tubing, and means for introducing fluid to be stored into said cavern.

4. In an underground storage system, in combination, an underground storage cavern having at least the top portion thereof defined by a substerranean impermeable formation, a shaft extending from the surface of the earth through said formation to a region adjacent said cavern, a tunnel connecting said shaft with the bottom region of said cavern, and sealing means sealing off said shaft at a level adjacent the top of said formation, said sealing means including a tubular metal liner having its lower end extending slightly below the top of said formation and having its upper end extending slightly above the top of said formation, a mass of cement anchoring said liner in position within said shaft, a flat plate closing off the top of said liner, a casing string extending from the surface downwardly through said shaft and said plate to the level of the bottom of said tunnel, a string of tubing mounted concentrically within said casing string, a motorpump unit carried by said tubing and positioned thereby at the bottom of said casing to lift the fluid from said cavern to the surface through said tubing, and a motor valve in said casing string at a point above said flat plate, said valve being operable to close the casing when the pump unit has been pulled up sufliciently to clear said valve.

5. A combination in accordance with claim 3 further comprising a filler pipe extending from the surface of the earth through the subterranean formations to the top of said cavern, said filler pipe having a horizontally disposed perforated portion extending horizontally adjacent the top of said cavern so that liquid fed through said pipe enters the cavern in the form of a spray and thereby cools vapors present in said cavern to reduce the filling pressure.

6. In an underground storage system, in combination, an underground storage cavern, a shaft extending from the surface of the earth through said formation to said cavern, means sealing off said shaft at a level adjacent the top of said cavern, said sealing means including a tubular metal liner, a mass of cement anchoring said liner in position within said shaft, and a flat plate closing off the top of said liner, the upper end of said liner having a tapered portion so that the liner is of progressively less thickness proceeding toward the top thereof, an annular member disposed concentrically within the top portion of the liner and welded thereto a gasket disposed between said plate and said annular member, and a plurality of screws securing said plate to said annular member.

7. In an underground storage system, in combination, an underground storage cavern, a shaft extending from the surface of the earth to said cavern, means sealing off said shaft including a tubular metal liner having its lower end extending slightly below the top of said cavern and having its upper end extending slightly above the top of said cavern, a mass of cement anchoring said liner in position within said shaft, a flat plate closing off the top of said liner, a first casing string extending from the surface of the earth downwardly through said shaft and through said plate, means for withdrawing said fluid from the bottom of said shaft including a downhole pump and a conduit extending from the pump discharge through said first casing string to the surface, a second casing string extending from the surface of the earth downwardly through the substerranean formations to the top of said cavern, a tubing string disposed concentrically within said second casing string, means for introducing fluid to be stored in said cavern into said tubing, a vent valve at the surface communicating with the interspace between said tubing and said second casing, and a motor valve in said first casing string at a point above said flat plate, said motor valve being operable to close said first casing string when the pump unit has been pulled up sufficiently to clear said motor valve.

8. in an underground storage system, in combination, an underground storage cavern having at least the top portion thereof defined by a subterranean impermeable formation, a shaft extending from the surface of the earth through said formation to a region adjacent said cavern, a tunnel connecting said shaft with the bottom region of said cavern, means sealing off said shaft at a level adjacent the top of said formation, said sealing means including a tubular metal liner having its lower end extending slightly below the top of said formation and having its upper end extending slightly above the top of said formation, a mass of cement anchoring said liner in position within said shaft, and a flat plate closing off the top of said liner, means for introducing fluid to be stored into said cavern, means including a down hole pump and a casing string extending upwardly through said shaft and said plate to lift fluid from the cavern to the surface, a hoist, and means for raising and lowering said hoist in the shaft.

9. in an underground storage system, in combination, a plurality of underground storage caverns, a shaft extending from the surface of the earth to a region adjacent all of said caverns, tunnels connecting said shaft with the respective bottom regions of said caverns, sealing means in said shaft immediately above the level of the top of said caverns, said sealing means being constructed and arranged to close off said caverns and prevent escape of vapors from the caverns into the top part of the shaft, means for introducing fluid to be stored into said caverns, means including a down hole pump and a line extending from the discharge of said pump through said sealing means to the surface for lifting fluid from said caverns, a hoist, and means for raising and lowering said hoist in said shaft.

10. In an underground storage system, in combination, a plurality of underground storage caverns, a shaft extending from the surface of the earth to a region adjacent all of said caverns, tunnels connecting said shaft with the respective bottom regions of said caverns, sealing means in said shaft immediately above the level of the top of said caverns, said sealing means being constructed and arranged to close off said caverns and prevent escape of vapors from the caverns into the top part of the shaft, said sealing means including a tubular metal liner having its lower end extending slightly below the top of said formation and having its upper end extending slightly above the top of said formation, a mass of cement anchoring said liner in position within said shaft, and a fiat plate closing off the top of said liner, means for withdrawing said fluid from the bottom of said shaft including a downhole pump and a conduit extending from the pump discharge through said plate and said shaft to the surface, a casing string extending from the surface of the earth downwardly through the subterranean formations to the top of one of said caverns, a tubing string disposed concentrically within said casing string, means for introducing fluid to be stored into said tubing, and a vent valve at the surface communicating with the interspace between said tubing and said casing.

11. In an underground storage system, in combination, an underground storage cavern, a shaft extending from the surface of the earth to a region adjacent said cavern, a tunnel connecting said shaft with the bottom region of said cavern, a liner anchored in said shaft, the upper end of said liner extending slightly above the top of said cavern, the region of said shaft above said liner being in unobstructed communication with the atmosphere, sealing means across said liner at a region slightly above the top of said cavern, and a casing extending from the surface of the earth through said shaft and said sealing means to a position adjacent the level of the bottom region of said cavern so that fiuid can be withdrawn from the cavern through said casing.

References Cited in the file of this patent UNITED STATES PATENTS 

11. IN AN UNDERGROUND STORAGE SYSTEM, IN COMBINATION AN UNDERGROUND STORAGE CAVERN, A SHAFT EXTENDING FROM THE SURFACE OF THE EARTH TO A REGION ADJACENT SAID CAVERN, A TUNNELL CONNECTING SAID SHAFT WITH THE BOTTOM REGION OF SAID CAVERN, A LINER ANCHORED IN SAID SHAFT, THE UPPER END OF SAID LINER EXTENDING SLIGHTLY ABOVE THE TOP OF SAID CAVERN, THE REGION OF SAID SHAFT ABOVE SAID LINER BEING IN UNOBSTRUCTED COMMUNICATION WITH THE ATMOSPHERE, SEALING MEANS ACROSS SAID LINER AT A REGION SLIGHTLY ABOVE THE TOP OF SAID CAVERN, AND A CASING EXTENDING FROM THE SURFACE OF THE EARTH THROUGH SAID SHAFT AND SAID SEALING MEANS TO 